This paper is mainly concerned with the saturated-unsaturated seepage analysis of embankment dams based on unsaturated soil theory and the reliability analysis of embankment dam based on conception of reliability. The transient seepage due to change of the water level is calculated using the finite element method based on unifying saturated-unsaturated seepage governing equations. The transient pore water pressures are then used for stability analyses of embankment dam considering the effects of suction on shear strength of unsaturated soils. Meanwhile, combined with reliability computation, the Monte-Carlo stimulation method is used to calculate the corresponding reliability index dealing with the stochastic features of soil parameters. The reliability of different water level condition of embankment dams has been analyzed. The effects of different reservoir water level drawdown and raise speeds on reliability of embankment dam are discussed.